1. Field of the Invention
The present invention relates to bubble levels. More particularly, the present invention relates to a bubble level with a bubble that can be seen from a distance and that can indicate when a longitudinal axis of the bubble level is substantially horizontal, regardless of how the bubble level is rotated about the longitudinal axis.
2. Description of Prior Art
Bubble levels are widely used to help people ensure items are substantially level or upright. For example, people commonly use bubble levels to properly align and level pictures being hung on walls and studs used to form walls in houses and other buildings.
Additionally, when building structures, people often use bubble levels to check that individual components of such structures are horizontal. For example, when building a deck, people often use bubble levels to ensure that cross members are horizontal so that the deck will be level.
Commonly available bubble levels use a cylindrical tube partially filled with liquid. Such tubes are typically slightly bent in order to force a high point within the tube. A bubble in the liquid indicates when these bubble levels are substantially horizontal, by seeking the high point.
These bubble levels work well, but only when they are used with a top side oriented upwardly. If these bubble levels are flipped upside down, so that the top side is oriented downwardly, they no longer function properly. This is due to the fact that what should be the high point is now a low point.
Additionally, if these bubble levels are rotated approximately ninety degrees, so that the top surface is oriented to one side, they no longer function properly. This is due to the fact that there is no longer a high point within the tube.
In order to overcome these limitations, manufacturers are forced to install several of these tubes into each bubble level. However, more tubes increases manufacturing costs making such bubble levels more expensive. Additionally, more tubes increases the complexity of such bubble levels by requiring a user to decide which tube he or she should observe. Furthermore, more tubes increases the size and weight of such bubble levels.
An additional limitation of commonly used bubble levels is an inability to see them from a distance. Bubbles in these bubble levels are typically not able to reflect or direct light toward a user and thus are not visible unless the user is very close by.
Accordingly, there is a need for an improved bubble level that overcomes the limitations of the prior art.
The present invention overcomes the above-identified problems and provides a distinct advance in the art of bubble levels. More particularly, the present invention provides a bubble level with a bubble that can be seen from a distance and that can indicate when a longitudinal axis of the bubble level is substantially horizontal, regardless of how the bubble level is rotated about the longitudinal axis. The bubble level broadly comprises a base and a vial. The base includes two arcuate ends, two slightly outwardly bowed sides, and a substantially flat top surface.
The vial includes two substantially flat exterior ends, two slightly outwardly bowed exterior sides, and a substantially flat top exterior surface. The top exterior surface of the vial preferably includes graduations which are substantially centered with respect to the top exterior surface. The graduations preferably include indicia of a midpoint of the graduations.
In addition, the vial includes two inwardly sloped substantially flat triangularly shaped interior end-walls and two inwardly sloped outwardly bowed interior side-walls. The interior side-walls are aligned at an approximately forty-five degree angle to the exterior sides and the top exterior surface of the vial. Additionally, the interior side-walls meet slightly below the top exterior surface at an approximately ninety degree angle to form an arcuate apex along the longitudinal axis of the vial. The apex is closest to the top exterior surface of the vial near a middle of the top exterior surface. The apex curves slightly away from the top exterior surface as it nears the two interior end-walls of the vial. The middle of the vial is preferably aligned with the midpoint of the graduations.
During manufacturing, a liquid is injected between the base and the vial through a hole in the base in sufficient quantity so as to form the bubble. The bubble is preferably large enough so as to not be able to form a true spherical shape at any point between the base and the vial.
Light incident upon either of the interior side-walls where the bubble is present meets an air interface at the approximately forty-five degree angle of the interior side-wall. The air interface causes the light to reflect at an approximately ninety degree angle. Therefore, light entering the top exterior surface will be reflected off one of the interior side-walls adjacent the bubble and out one of the exterior sides of the vial. This is particularly useful in gathering and reflecting sunlight or other ambient light so that the bubble can be seen from a greater distance.
Additionally, when light is incident upon either one of the exterior sides or the top exterior surface of the vial, from within the vial, a portion of the light is reflected. Thus, when light enters one of the exterior sides of the vial and becomes incident upon one of the interior side-walls, it is reflected toward the top exterior surface of the vial. When the light is incident upon the top exterior surface, from within the vial, a portion of the light is reflected back toward the interior side-wall. The light is again reflected off the interior side-wall toward the exterior side of the vial.
These air interfaces allow a user to look into one of the exterior sides of the vial and align the bubble with the midpoint of the graduations on the top exterior surface of the vial. Thus, the user may view the position of the bubble with respect to the graduations, by looking at either of the exterior sides or the top exterior surface of the vial. Additionally, the user may view the bubble within the bubble level from a distance, since light can be gathered and reflected toward the user. For example, if one of the exterior sides is aligned upwardly, then light entering the exterior side may be reflected out the top exterior surface to the user who may be standing across a room from the bubble level.
When the longitudinal axis of the bubble level is substantially horizontal, the bubble will be substantially centered with respect to the graduations and thereby indicate that the bubble level is level. As will be discussed below, this is true without regard to how the bubble level is rotated about the longitudinal axis.
For example, when the bubble level is rotated so that the top exterior surface is aligned upwardly, the bubble is centered due to the fact that the middle of the apex is closest to the top exterior surface of the vial. Therefore, a highest point is directly under the midpoint of the graduations.
As another example, when the bubble level is rotated so that either one of the exterior sides is aligned upwardly, the bubble is centered due to the fact that the interior side-walls are bowed outwardly, as discussed above. Therefore, the highest point is where a middle of the interior side-wall meets the base. The middle of the interior side-wall is also aligned with the graduations, such that the bubble is centered adjacent the midpoint of the graduations.
As a final example, when the bubble level is rotated so that the top exterior surface is aligned downwardly, the bubble is centered due to the effect of surface tension acting upon the bubble and against the interior side-walls. Since the top surface of the base is substantially flat, there is no highest point on the top surface of the base. Additionally, since the middle of the apex is closest to the top exterior surface, the middle of the apex is now a lowest point in the vial. Therefore, the middle of the apex is farthest from the base and provides a maximum cross-sectional area between the base and the vial. The maximum cross-sectional area allows the bubble to most closely achieve the spherical shape, which is the shape the surface tension of the liquid inherently tries to achieve.
Therefore, by constricting the area between the base and the vial such that the bubble cannot achieve the spherical shape, the surface tension of the liquid will center the bubble with respect to the graduations. This is due to the fact that the bubble is able to most closely achieve the spherical shape only when the bubble is centered with respect to the middle of the apex, which is centered with respect to the midpoint of the graduations. Thus, the surface tension of the liquid causes the bubble to indicate that the bubble level is level, when there is no highest point for the bubble to seek.
The operation of the bubble level has been described as the bubble level is rotated about a substantially horizontal longitudinal axis, in approximately ninety degree increments. As should be apparent, when the bubble level is rotated to a point between one of the above described examples, a combination of the above principals will act to center the bubble. This, of course, is provided that the longitudinal axis of the bubble level is held substantially horizontal.
Alternatively, when the longitudinal axis of the bubble level is not substantially horizontal, the bubble will not be substantially centered with respect to the graduations. This is due to the fact that the highest point is located other than adjacent the midpoint of the graduations without regard to how the bubble level is rotated about the longitudinal axis. The degree to which the longitudinal axis is not horizontal can also be indicated by the bubble and the graduations.
In use, the user affixes the bubble level to the object to be leveled. Alternatively, the user may simply hold the bubble level against the object, or may place the bubble level on top of the object, letting gravity hold the bubble level in place. Then, the user looks into the vial from either of the exterior sides or the top exterior surface of the vial and moves the object to center the bubble with respect to the midpoint of the graduations. Regardless of whether the user looks into the vial from either of the exterior sides or the top exterior surface, the user can seen the graduations using the reflective properties of the vial, as described above.